How to protect your galvanized steel pipe from white rust in applications

In the modern times, galvanized steel pipe are widely used in a variety of applications from building materials to infrastructure projects. However, once the galvanised surface has been attacked and the zinc hydroxide compounds have formed, it is desirable to remove the oxide products from the surface because:1) their presence inhibits the formation of stable carbonate based oxides; 2) they are unsightly.

In most cases, the effect on the galvanised coating can range from very minor to extremely severe and various levels of remedial treatment are available to deal with white rust problems at the various levels at which they are likely to occur. DongPengBoDa Steel Pipe Group is one of the professional steel pipe manufacturers in China. Here we would like to give you a few helpful treatments for your galvanized steel pipe in use.

First, if your galvanized steel pipe has light white rusting during periods of heavy rain. It is particularly evident on areas that have been buffed or filed during quality assurance operations. These treatments remove the passivated surface from the galvanizing and expose unoxidised zinc to attack from rainwater. Provided the items are well ventilated and well drained, white rust rarely progresses past this superficial stage. It can be brushed off if required but will generally wash off in service with normal weather. No remedial treatment is generally required for this level.
Second, for pre galvanized steel pipe used in structural frames, if there occurs a noticeable darkening and apparent etching of the galvanised coating under the affected area, with the white rust formation appearing bulky. The galvanised coating thickness should be checked to determine the extent of attack on the coating. In the majority of cases, less than 5% of the galvanised coating will have been removed and thus no remedial work should be required as long as the appearance of the affected area is not detrimental to the use of the product and the zinc hydroxide residues are removed by wire brushing. If appearance is unacceptable, the white rust affected area can be treated as follows:
•Wire brush the affected area to remove all white corrosion products
•Using a cloth pad wet with aluminium paint, rub the surface with the pad to apply a thin film of aluminium paint to the affected area to blend it with the adjacent unaffected galvanised surfaces.

Lastly, for steel conduits used in wire systems, if your galvanized steel pipe has severe white rusting, areas under the oxidized area may be almost black and show signs of red rust. A coating thickness check will determine the extent to which the galvanised coating has been damaged. Remedial treatment to reinstate the coating should be undertaken as follows:
•Wire brush or buff the affected area to remove all oxidation products and rust if any.
•Apply one or two coats of approved epoxy zinc-rich paint to achieve required dry film thickness of 100 microns minimum.